1. 7.2 The Constellation
Homework: Page 282 # 1,4,6,7

2. Key Concepts:
Constellations are groupings of stars that form distinctive patterns. The stars in these groupings appear to be close to each other but they are not.
A star’s apparent magnitude is its brightness as seen from Earth.
The Big Dipper is an asterism, which is a smaller grouping of stars within a constellation.

3. Earth’s rotational axis points to Polaris, the North Star
Earth’s rotational axis points to Polaris, the North Star. For thousands of years, travellers have used Polaris and the constellations to navigate.
Different cultures have different interpretations of the night sky.
A light year is the distance that light travels in one year.

4. Constellations Two Definitions:
Astronomical – a region in the sky
Traditional - A group of stars observed from Earth often forming shapes.
Constellations are the signs of the zodiac, mythological figures and other shapes.

5. The Stars are Moving…
We are still able to see the same constellations as the ancient people, however the stars are not in the exact same location as they once were. This is because the stars are moving away from each other due to the expanding Universe.
Also, because of Earth’s rotation the stars (and the constellations) always appear to be moving in the sky.

6. Pointer Stars…
The two stars at the end of the bowl of the Big Dipper are called the "Pointer Stars" because a line drawn between them points to Polaris, the North Star.
The Big Dipper is a asterism, ( a smaller grouping of stars within a constellation). It is circumpolar, which means it stays above the horizon all night long as it apparently rotates around Polaris due to the Earth's rotation.

7. Star Maps
Show the relative positions of the stars in a particular part of the sky.
Star maps represent stars by dots of varying sizes. The larger the dot, the brighter the star is.
The term apparent magnitude is used to describe the brightness of a star.
A star’s apparent magnitude is its brightness seen from Earth.

8. The Celestial Sphere
It is the imaginary sphere that rotates around Earth, onto which all celestial objects are projected.
Due to the Earth’s rotation around the Sun, you see different constellations in the evening sky at different times of the year.
The constellations also depend on their latitude. As you move northward, constellations along the southern horizon slip below the horizon so you cannot see them. As you move southward, constellations formerly unseen, rise above the southern horizon.

9. Navigation using Stars
Celestial navigation – the use of positions of stars to determine location and direction when travelling.
The Big Dipper and Polaris played an important part in the story of the Underground Railroad which helped slaves escape their captivity by fleeing north to Canada.

10. Culture Connection
Mayans – built a pyramid (El Castillo) and on the solstices at sunset the shadow formed looks like a snake
Stonehenge – may have been used to predict the motions of the Sun (an astronomical calendar)
Aboriginals – have many legends relating to astronomy (stars formed because the Sun spit sparks, lunar eclipses because monsters swallowed the Moon, the Sun goes to sleep so its brother the Moon rises in the east to give light during the night)